The invention concerns a water steam sterilizer, a so-called autoclave.
Such devices are especially required in the medical field and, because of the constant increasing resistance of germs, must enforce increasingly costlier sterilisation procedures.
Of this fact, considering present days requests, it is absolutely necessary practically world wide that, at the beginning of each sterilisation cycle, the initially existing air in the chamber and the load is essentially completely removed by a specific procedure consisting in successive vacuum and pressure pulses called fractionate vacuum.
This means, that after a first vacuum phase and heating up, steam must be injected in the chamber in order to grow up internal temperature and pressure ( greater than 0 bar relative, for practical reasons the pressure is always given in relation to the atmospheric pressure). Then the chamber is drained before a successive vacuum phase in initiated. This is repeated a number of times, until the sufficient expulsion of the initial air is guaranteed.
First then the next phase, the initialisation of the sterilisation procedure will start, with more highly than until now reached temperature and corresponding pressure.
It is clear that a longer time is required, also the quantity of the necessary energy as well as the water consumption increase significantly, since several chamber filling and drain are required, without that these can be considered as sterilisation phases.
Also beside the duration, attention must be given in particular to the energy and also the water consumption (main water cannot be used).
An appliance corresponding nearly to this type of technology, is described in the DE 44 45 054 C2. The applicance in accordance to this document uses a non water cooled condenser and also a water free working vacuum pump.
By the way, it fulfills some of the above mentioned conditions. The disadvantage of this appliance, which however is not detailed in the specified document, is that during the starting, between each vacuum and pressure pulse (phase), not only the chamber is drained, but also the steam generator.
This means that, firstly a big quantity of water and energy required to generate steam is wasted, and secondly a corresponding time is necessary to rebuilt steam and reach again the process parameter for the next pressure pulse.
Of course, it is possible to reduce the time losses by using powerful heating systems, however this changes nothing regarding energy and water losses or better to say wasting.
Consequently, the goal of the invention is to provide an autoclave, and its principle of functioning, avoiding the listed disadvantages and able to manage the predetermined vacuum and pressure pulses using less water and energy, this without increasing the duration of the cycle.
Due to the invention, the goals are reached principally by using valves placed between the chamber and the steam generator and between the chamber and the condenser/vacuum pump group. During the chamber drain phases, the valves insulate completely the chamber from the steam generator in order not to drain it and that the air/steam/water mixture crosses the condenser and the vacuum pump, before to be drained in the used water tank.
As vacuum pump, preferably a membrane vacuum pump is used due to its ability to suck air, steam or water as well as any air/steam/water mixture.
In an preferred embodiment. The device is additionally equipped with a so called condensation accumulator in order to extract the condensed steam (water) from the chamber and at regular intervals drain it in the steam generator to be heated up again.